In order to meet the wireless data traffic demand that is on an increasing trend after commercialization of 4G communication system, efforts for developing improved 5G communication system or pre-5G communication system have been made. For this reason, the 5G communication system or pre-5G communication system has been called beyond 4G network communication system or post LTE system.
In order to achieve high data rate, implementation of 5G communication system in a millimeter Wave (mmWave) band, for example, 60 GHz band, has been considered. In order to mitigate a radio wave path loss and to increase a radio wave transmission distance in the mmWave band, technologies of beam-forming, massive MIMO, full dimension MIMO (FD-MIMO), analog beam-forming, and large scale antenna for the 5G communication system have been discussed.
Further, for system network improvement in the 5G communication system, technology developments have been made for an evolved small cell, advanced small cell, cloud radio access network (cloud RAN), ultra-dense network, device to device (D2D) communication, wireless backhaul, moving network, cooperative communication, coordinated multi-points (CoMP), and reception interference cancellation.
In addition, hybrid FSK and QAM modulation (FQAM) and sliding window superposition coding (SWSC), which correspond to advanced coding modulation (ACM) system, and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA), which correspond to advanced connection technology, have been developed in the 5G system.
On the other hand, with the rapid spread of wireless communication devices, demand for mobile communication data has been abruptly increased. In order to cope with such abruptly increased demand for mobile communication data, various technologies for improvement of a data rate have been developed. As one method for improvement of the transfer rate and increase of the capacity of a wireless communication system, there is a method for performing communication through increasing the number of antennas between a transmitter and a receiver.
The technology to increase the system capacity using a large number of antennas has the advantage that the performance of the system is increased in proportion to the number of antennas provided in a transceiver. However, in an actual environment, due to constraint requirements of a terminal having limitations in physical size, there is a limit in increasing the number of antennas, and due to this, it is not possible to increase the transmission capacity through a point-to-point MIMO technology. In order to overcome this, a multi-user MIMO (MU-MIMO) scheme has been introduced, which heightens a downlink transfer rate through a point-to-multipoint technology in which a large number of antennas are mounted on a base station having a large physical size and data is simultaneously transmitted to a plurality of terminals.
Since the MU-MIMO system transmits signals simultaneously to several users, interference between the users who receive the signals may deteriorate the performance, and in order to overcome this, a technology capable of controlling the interference between the users is necessary. The transmitter may acquire channel information of the multiple users, and may perform precoding for controlling the interference to make MU-MIMO transmission possible. In this process, the transmission end surely requires channel information of the receiver to which the transmission end intends to transmit the signal. In the case of a wireless network using a TDD, the transmission end acquires the channel information through an uplink reference signal. In contrast, in the case of a wireless network using an FDD, the transmitter acquires the channel information in a manner that the receiver estimates the channel information and feeds the estimated channel estimation back to the transmitter through uplink transmission.
Even an L (or LTE-Advanced) system, which is mostly used for cellular communication, adopts a technology in which the receiver feeds back channel information and the transmitter uses the channel information to perform MIMO/MU-MIMO transmission.
On the other hand, antennas having various shapes may be used in a wireless communication device, and cross polarization (XPOL) antennas in a rectangular panel shape (2D) are mostly used. The XPOL antennas, the number of which is double the number of co-polarization (COPOL) antennas, can be arranged in the same space as compared with the COPOL antennas, and thus they are efficient for multi-antenna transmission.
Further, the channel information feedback technology as described above should be designed so as to well reflect the wireless channel characteristics, and the wireless channel characteristics are affected by the antenna shape. That is, in the case of assuming a transmitter using the XPOL antenna, it is essential to design a channel information feedback that suits the XPOL antenna. Even in the LTE system, feedback designs that suit both the COPOL antenna and the XPOL antenna have been considered.
Up to now, most MIMO-MU-MIMO technologies have been designed on the assumption of one-dimensional (1D) arrays in which antennas are one-dimensionally configured, and antenna installation and MIMO scheme application in a horizontal dimension having various user distributions have been mainly considered. However, recently, as the user distribution in a vertical dimension is increased in an urban environment in which many high-rise buildings are distributed, development of a three-dimensional (3D) MIMO scheme using a two-dimensional (2D) array has been concerned. In the case of applying the 2D array to the MIMO transmission, it is essential to design a channel information feedback scheme in consideration of this.
However, up to now, a channel information feedback scheme for utilizing a 2D array has not yet been proposed.